The Apple IIc brand computer is a highly-compact version of the ubiquitous Apple II brand series of personal computers which, through Apple Computer's marketing wizardry, has become the defacto standard in personal computers for educational use. The Apple IIc, avaiable with a flat, low-energy-consumption, liquid-crystal-display screen, comes complete with a built-in, half-height 51/4-inch floppy disk drive. The only feature which the Apple IIc lacks to become a true portable is a rechargeable, battery-driven power supply.
The Apple IIc computer is normally powered by a free-standing power source which converts 115-volt AC line current to 15 volts DC which is then fed into the rear of the computer. Like all computers dependent on AC current from the power line, the Apple IIc is, in its standard form, vulnerable to interruptions in the supply of AC current. Although the read-write head of the DC-powered floppy disk drive of the Apple IIc is not subject to loss of control resulting in a corruption of data on the diskette tracks over which it hovers when the power either fails or is restored, a loss of power for a fraction of a second--or even a substantial voltage drop--can cause unrecoverable data loss from dynamic memory. Given this vulnerability to power interruptions, an uninterruptible power supply would be very beneficial.
A problem of uninterruptible power supplies powered by batteries is that a computer user may easily discharge the batteries beyond the optimum discharge point, resulting in greatly-shortened battery life and possible damage to the computer. Ideally, an uninterruptible power supply would alert the user to a low-voltage situation, provide him with enough time to save his work product, and then automatically cut off the power to the computer.